Facial Nerve Surgery

Anatomy

The facial nerve (seventh cranial nerve) is the primary nerve for movement of the facial muscles. It also provides taste to the anterior two thirds of the tongue.

 

From the brainstem, the nerve enters the temporal bone, runs in the middle ear, then exits the skull to enter the parotid salivary gland. It divides in the parotid into five main branches, which innervate the facial muscles. In the temporal bone the facial nerve runs in a bony canal (fallopian canal).

Facial surgery

Bell’s Palsy

The etiology of Bell’s palsy is unknown, although current believe is that it is caused by a Herpes simplex virus infection. Other viruses may also be involved.

 

The infection and subsequent inflammation cause swelling of the nerve in the fallopian canal. This swelling causes a compartment syndrome in the bony canal and damage to the nerve.

 

A sudden onset (in 48 hours) of unilateral facial paralysis develop. The paralysis may be complete or partial. Sometimes symptoms like ear pain, taste disturbance, tearing of the eye and numbness in the face, are associated. The paralysis usually clears up completely in a few weeks. A partial paralysis tends to have a better prognosis. Sometimes Bell’s palsy may be recurrent (the same or the other side) and rarely bilateral.

 

Other causes (like tumors and infections) need to be excluded.

 

The treatment consists of antiviral medication, cortisone and protection of the eye (drops, patch). Surgical decompression of nerve may be used in severe damage to the nerve, although it remains controversial. 

 

Ramsey Hunt Syndrome

This is shingles of the ear. The same virus (varicella zoster) that causes chicken pox, lie dormant in nerves. When your immunity drops (stress, diabetes or HIV), the virus becomes active and causes damage to nerves. When the facial nerve is affected, it is called Ramsey Hunt syndrome. Sometimes the hearing and balance nerve may also be affected. Patients present with a facial nerve paralysis, ear pain and vesicles/sores/crusting in the outer ear. This condition is much more aggressive than Bell’s palsy. Treatment of antiviral drugs and cortisone are used. Severe pain is also treated.

 

Tumors

Primary tumors of the facial nerve or secondary tumors may cause damage to the nerve. Primary facial nerve tumors are usually Schwannoma’s. These are benign tumors arising from Schwann cells in the nerve. Acoustic neuroma’s or Schwannoma’s from the balance nerve (lie next to the facial nerve) may cause damage to the facial nerve. Other tumors along the course of the facial nerve may also affect it. These include brain tumors, tumors of the temporal bone/ ear, skull base and parotid gland.

 

Facial palsy due to tumors is usually progressive and ticks/ jerks of the face may be associated.

 

Infections

Besides primary viral infections infections of the nerve, surrounding infections may cause paralysis. Intracranial infections like meningitis or middle ear infections (otitis media) with mastoiditis may cause damage. Cholesteatomas, severe outer ear infections (malignant otitis externa) or even infections of the parotid salivary gland may be a cause of facial nerve paralysis.

 

Hemifacial Spasm

This is a condition where the facial muscles get periodic spasms. It is usually unilateral although a small percentage may be bilateral. It starts of with spasms around the eye and progress to involve the whole face. An aberrant blood vessel in the brain (anterior inferior or posterior inferior cerebellar artery) compresses the facial nerve as it exits the brain.

 

The treatment is medication (carbamazepine etc.), Botox injections or surgery.

Surgery

Exploration of the facial nerve in its fallopian canal to decompress the nerve (release the compartment syndrome). When the facial nerve is disrupted due to trauma, tumors or tumor surgery, facial nerve repair is used to restore facial nerve function. A few options are available. If there is no or minimal loss of nerve length, the two disrupted nerve ends are approximated with sutures. If a part of the nerve is lost, a graft from another nerve (greater auricular or sural nerve) is used and sutured between the two ends of the facial nerve. In some cases, the proximal section (brain part) of the nerve is lost. In these cases, another nerve is used to stimulate the lower facial nerve and facial muscles. Several options are available, of which the hypoglossal (tongue muscle) nerve is the best option. About a third to a half of the hypoglossal nerve diameter is cut. This end is then connected via a graft to the lower end of the facial nerve. Around a two third recovery of the face is expected after 12 to 24 months.